What is the immortal jellyfish?

The immortal jellyfish, scientifically named Turritopsis dohrnii, is a tiny species of jellyfish. It's so small that an adult is about the size of your pinky fingernail. It gets its famous name from its remarkable ability to avoid death from old age.

How does it work? The life cycle

1. In the beginning of it's life, the jellyfish is a larva. It's just a simple bundle of cells. This larva swims around until it finds a good place to settle down, like a rock or a dock.

2.  When the larva settles, it attaches itself to a surface and grows into a plant-like creature called polyp.

3. When the adult immortal jellyfish is stressed by things like injury, old age, or not having enough food, it can choose to "reset" its life. It pulls its tentacles and bell back into a small piece of tissue.

4. This blob of tissue then attaches itself to a surface and grows back into a new polyp colony, the very first stage of its life. It has essentially reversed its aging and started its life cycle all over again.

This process can happen repeatedly, which is why scientists call the jellyfish "biologically immortal." It can escape death from aging and continuously rejuvenate itself.

Why is it not truly immortal?

While it can't die from old age, it can still be killed. The immortal jellyfish is very small, so it's a perfect meal for many animals like fish and turtles. It can also die from disease or if its environment suddenly changes. So, in the wild, most immortal jellyfish probably die before they get a chance to use their "reset" ability.

Where is it found?

The immortal jellyfish is originally from the Mediterranean Sea. Though it can also be found in other places